A significant problem in the field of dentistry has been to remove stain from the surface of a patient's teeth even after a thorough prophylaxis (cleaning) has been completed. Many different types of devices have been proposed for this type of stain removal. One class of such devices includes a hand held tool having inputs for air and water under pressure and a spray nozzle for directing the air and water mixture at the tooth. Such tools usually also include a box or chamber for mixing an abrasive powder with the air so that the nozzle produces a spray consisting of an abrasive-laden air stream mixed with water, as shown, for example, in Nelson et al. U.S. Pat. No. 4,540,365. The Nelson tool includes a mixing chamber in the handle in which air agitates particulate matter in the chamber causing it to flow as an abrasive-laden stream towards an orifice. The Nelson device, however, includes a mixing chamber which is interior to the handle. It is thus awkward and difficult to load the abrasive material into the mixing chamber. Also, with the Nelson device, water and an abrasive-laden air stream are mixed prior to the exit from the nozzle. This is undesirable because a wet slurry is formed inside the nozzle which may clog the entrance and which is less precisely directed by the nozzle.
A similar device is shown in the U.S. Pat. to Conger, No. 4,648,840 which includes a pencil-like handle which includes a downwardly-extending canister for holding an abrasive powder, and a nozzle having an interior conduit for carrying an abrasive-laden air stream surrounded by a conduit for carrying water. The two streams are mixed at the forward end of the conduits. The Conger device is more easily loaded with abrasive powder than is the Nelson device, because the downwardly-extending canister may be unscrewed from the handle. The way in which the Conger device is held, however, makes it awkward to use. The handle of the Conger device is adapted to be grasped like a pencil but the downwardly-extending canister can make its use inconvenient. Also, the body of the Conger device is too large for it to be easily grasped in this manner. A similar device is shown in European Patent Application No. 0,163,610 published Apr. 12, 1985.
In yet another patent, Black, U.S. Pat. No. 3,972,123, a nozzle is shown which includes an outlet for an air/abrasive mixture and water outlets surrounding the air/abrasive outlet tilted toward the abrasive outlet so that the water streams converge on the abrasive-laden air stream. This system, however, is undesirable because such an arrangement creates a pinpoint stream which concentrates both streams at a particular point on the tooth and does not fan out over the surface of the tooth.
What is needed therefore is a dental cleaning tool of the type utilizing an air/abrasive stream surrounded by a water curtain that may be easily grasped and controlled, and having a nozzle which ensures that the air/abrasive-water mixture will fan out across the area to be cleaned.